The present invention relates to a control apparatus for an automatic pipe welder, and more particularly to a control command generating circuit suited to a control apparatus for an automatic pipe welder.
Recently, an automatic pipe welder which butt welds pipes while running along the circumference of the pipe has been frequently used. When the pipes are butt welded by such a welder, gravity applied to the molten metal changes with the position, at which the welder is running while welding, on the periphery of the pipe. Accordingly, it is a common practice to change the welding conditions such as welding current, welding voltage, feeding speed of a welding wire, welding velocity, weaving pattern and the like, depending on the welding position. To this end, as many potentiometers as the number of conditions to be changed are required for setting the welding conditions on respective positions on the periphery of the pipe. Further, in case of multi-layer welding where one joint is welded through several welding steps, the welding conditions may be changed from layer to layer. In such a case, potentiometers for setting the welding conditions on the respective positions for every layer are required. Since the number of potentiometers required is great, a control panel therefor must be of large size and wiring thereof must be very complex. In addition, the construction of a circuit for issuing commands for changing the welding conditions by switching the outputs of the potentiometers from layer to layer and from position to position on the periphery of the pipe must be also complex because of switching of analog voltages. In the light of the above disadvantages, it has been suggested to introduce a computer in the control apparatus for the automatic welder. However, the application of the computer particularly suitable for the control apparatus of the automatic pipe welder has not been proposed. If the computer is simply introduced with general purpose input/output devices, the configuration of the control apparatus would be complex and of large size. Also, if the welding conditions to be represented by the potentiometers are stored in a storage device of the computer and simply read out in a sequential manner, the availability of the computer would be lowered.